U.S. Pat. No. 3,896,131 describes a broad class of 6,7-dihydro-5-methyl-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acids as antimicrobial agents. The patent specifically discloses many compounds substituted by common substituents on the benzo ring. It has now been found that compounds substituted at the 8 position of the benzo ring by an imidazole ring exhibit enhanced antimicrobial activity.
Japanese patent application No. 106776 which was published Aug. 22, 1979, discloses benzo[ij]quinolizines having a heterocyclic piperazino group substituent on the benzo[ij]quinolizine ring. Compounds in which one of nitrogen atoms of the piperazino group is substituted are also disclosed.